The present invention relates generally to filing cabinets having drawer locking mechanisms for preventing the opening of drawers in the cabinet under certain conditions. More particularly, the invention relates to a filing cabinet having a remote locking device for locking drawers as a security measure in combination with an interlock mechanism which prevents the opening of more than one drawer at a time.
Conventional filing cabinets generally contain two or more horizontally sliding drawers to store files or other materials. With such filing cabinets, the opening of two or more drawers at one time may cause the cabinet to topple over. This is especially a problem when one file drawer is heavily loaded. Furthermore, the weight of an open cantilevered drawer may cause the cabinet to lean forward to an extent that the other drawers, due to gravity, slide from their closed to open positions, thereby causing the cabinet to tip over.
In order to prevent tipping of a cabinet, interlock mechanisms have been provided to prevent a second drawer of the cabinet from being opened after a first drawer has been opened. A common type of interlock system provides a vertically disposed latch bar that is positioned adjacent each drawer. As the drawer is opened, the latch bar moves into a position to prevent the other drawers from opening while the withdrawn drawer remains open. A problem experienced with this type of arrangement is that if two or more drawers are simultaneously moved to an open position, the latch bar can sometimes operate in the same manner as if one drawer is open. Therefore, no restraining effect on any of the moving drawers occurs, thereby resulting in possible tilting or tipping of the cabinet. This can be controlled to some extent by appropriate manual operation of the drawers, but if the files are improperly leveled and subject to vibrations, for example from adjacent machinery, the vibrations can induce simultaneous movement of several of the drawers to an open position to cause the file cabinet to tip over.
In addition to latch bars, other types of interlocking arrangements have been used. For example, the drawers may include channels which receive rollers secured to a vertically shiftable bar carried on the sides of the cabinet. In this arrangement, when one drawer is open, the roller displaces the vertical bar so that the rollers on the remaining drawers are no longer in registry with the channels on the bar. In this manner, the opening of a second drawer is prevented. Another type of interlock system includes the use of straps on the back surface of the drawers which engage vertical bars having corresponding locking portions. The vertical bars engage the strap at the back of the cabinet to prevent opening of a second drawer when a first drawer is open.
A problem with these systems is that the interlocking mechanisms are so critically aligned that there is no compensation for adjustments due to various loads on the cabinet. First, the bars or rods must be carefully aligned, which is often a time consuming procedure. In addition, the bars must be mounted at several locations on the drawer, which increases the chances of improper assembly. Further, these devices usually require a spring device that retains the bar in its position when the drawer is open. If the cabinet is bumped or jarred and a bar is misaligned, the cabinet essentially becomes inoperative. Problems may also occur in shipping. For example, if a cabinet is shipped, and the individual drawers are in an unlocked position, the bars can become misaligned so that the cabinet arrives at its destination in an inoperative condition.
Another type of interlock system uses a cam system. In these systems, a cam member is engaged and rotated as a drawer is opened to displace a stop mechanism (i.e. bar, belt, ballbearing, rod, rope, cable, etc.). One type of cam system utilizes a safety latch having vertical latch bars and rollers which cooperate with cam members attached to the sides of the drawers. When the drawer is moved, the cam member is displaced towards the roller so that the roller engages a cam surface on the latch bar and displaces the latch bar. The latch bar is then maintained in a displaced position to resist movement of a second drawer. Another type of cam system uses a ribbon or cable that is connected between the drawers and support on the frame of the cabinet. The cable has a predetermined slack which is taken up when the drawer is fully extended.
One problem with many of these cam systems is that the camming member utilizes a spring-biased detent, which holds the camming member in position while the drawer is open. However, if a drawer is partially open and the cabinet is moved or bumped before the force of the spring is overcome, the cam may rotate back to its closed position and prevent the drawer from being closed. In addition, another drawer may be opened.
Along with the problem associated with the spring biased camming member is that the cam systems are limited to use exclusively as an interlock. In order to lock the drawers for security reasons, an additional locking device is required.
It is desired to provide a drawer locking system in which both the interlock system and the remote lock system operate together. In addition, it is desired to provide a camming mechanism which avoids the problems associated with a spring loaded detent.